uva1439 Exclusive Access 2

<cstring> #include<algorithm> using namespace std; // Here n is the number of resources, m is the number of processes (n in the problem statement) const int maxn = 15; const int maxm = 100 + 5; int n, m, u[maxm], v[maxm], G[maxn][maxn]; int ind[1<<maxn], d[1<<maxn], best[1<<maxn], label[maxn]; bool independent(int mask) { for(int i = 0; i < maxn; i++) if(mask & (1<<i)) for(int j = 0; j < maxn; j++) if(mask & (1<<j)) if(i != j && G[i][j]) return false; return true; } // How many colors are needed to color the set ‘mask‘ int dp(int mask) { int& ans = d[mask]; if(ans >= 0) return ans; if(mask == 0) return 0; ans = maxn+1; for(int s = mask; s; s = (s-1)&mask) if(ind[s]) { int v = dp(mask^s) + 1; if(v < ans) { ans = v; best[mask] = s; } } return ans; } // mark the set ‘mask‘ with color c void mark(int mask, int c) { for(int i = 0; i < maxn; i++) if(mask & (1<<i)) label[i] = c; } int main() { while(scanf("%d", &m) == 1) { memset(G, 0, sizeof(G)); int useful = 0; for(int i = 0; i < m; i++) { char r1[9], r2[9]; scanf("%s%s", r1, r2); u[i] = r1[0]-‘L‘, v[i] = r2[0]-‘L‘; G[u[i]][v[i]] = 1; useful |= (1<<u[i]); useful |= (1<<v[i]); } // find the independent sets memset(ind, 0, sizeof(ind)); for(int s = useful; s; s = (s-1)&useful) if(independent(s)) ind[s] = true; // dp memset(d, -1, sizeof(d)); int ans = dp(useful); printf("%d\n", ans-2); // construct the answer int s = useful, k = 0; while(s) { mark(s, k++); s ^= best[s]; } for(int i = 0; i < m; i++) { if(label[u[i]] < label[v[i]]) swap(u[i], v[i]); printf("%c %c\n", ‘L‘+u[i], ‘L‘+v[i]); } } return 0; }

 

uva1439 Exclusive Access 2

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